NASA Weighs Late Heat Shield Inspections for Shuttle Crews

In this image made from NASA TV,astronaut Mike Fossum takes pictures of a farewell ceremony in the Destiny module of the International Space Station Saturday, July 15, 2006. The ceremony did not air on NASA TV. Commander Steve Lindsey, in foreground, and astronaut Lisa Nowak, center, watched from the background.

HOUSTON -NASA managers are discussing whether a late heat shield inspection that has madean already busy flight even more so for six astronauts aboard the shuttleDiscovery is worth the extra time and risk, a lead flight director saidSaturday.

TonyCeccacci, lead shuttle flight director for Discovery's STS-121 mission, saidflight planners and heat shield experts closely monitored the current crew over the last two days to determine whether the data gleaned from an additional inspection merits the extra rigors placed on orbiter astronauts.

"What we'retrying to see is how difficult this is to do and whether it's worth the risksof working the crew harder and such," Ceccacci said during a mission updatehere at Johnson Space Center (JSC). "We're using this as a good test to makesure we can accomplish this and accomplish this safely."

The finalinspections, which return up-close views of the reinforced carbon carbon (RCC)panels fixed to Discovery's nose and wing edges, are aimed at determiningwhether micrometeorites or other orbital debris have damaged the orbiter's heatshield during its eight days of docked operations at the International SpaceStation (ISS). If they turn up clear, Discovery will be given approval toland Monday, but if analysts find a large enough concern the orbiter's crew could return to theISS to seek shelter, NASA said.

At the sametime, engineers continueto watch the tank pressure in one of the orbiter's auxiliary power units(APU), which appears to be leaking either gaseous nitrogen or toxic hydrazinefuel. If the leak is hydrazine - it is not yet certain - and remains unchanged,it should not impact Discovery's planned Monday landing.

Discovery'sSTS-121 crew, commanded by veteran shuttle astronaut Steven Lindsey, undockedfrom the space station early Saturday at 6:08 a.m. EDT (1008 GMT). Afterpulling away from the station toward a station-keeping post some 40 nauticalmiles (74 kilometers) from the ISS, the shuttle astronauts went straight into afinal inspection of Discovery's starboard - or right - wing leading edge andnose cap using a sensor-equipped, 50-foot (15-meter) boom attached to the endof the shuttle's robotic arm.

The crewcompleted a similar survey of the spacecraft's port wing leading edge Friday,but delvedabout an hour into the sleep preparation to complete the task due to adelay caused by ISS robotic arm glitches.

Lindseyopted to push ahead with the task anyway, even when given the option to scrubit from the schedule altogether.

"We'relooking at the future flights to see what would be required to accommodate it,"Ceccacci said of the added inspections. "The more you take off the plate tocomplete the late inspection, now you're taking that out of the missiontimeline and now you have to find a place put that on a later mission. They maynot all line up, and have like a domino effect."

NASA has 15 planned shuttle missions, spread across its three remaining orbiters, to complete the ISS by 2010. The next flight, STS-115 to launch aboard Atlantis slated for a late-August launch, may also has room in its timeline for late heat shield inspections, Ceccacci said.

Discovery'sSTS-121 mission is NASA's second shuttle test flight since the 2003 Columbia accident, whichone orbiter and seven astronauts were lost due to a heat shield breach in thespacecraft's left wing leading edge caused by a 1.67-pound (0.7-kilogram) chunkof external tank foam the size of a briefcase.

The largestarea shed in Discovery's STS-121 launch weighed less than one ounce total,covered a space slightly larger than a legal-size piece of paper and fell offin stages of six smaller pieces, NASA has said.

But theagency remains vigilant in on-orbit inspections for shuttle heat shields. Discovery'scurrent STS-121 astronauts and those of NASA's first post-Columbia effort - STS-114 aboard the same orbiter- conducted intense, comprehensive scans of the shuttle's wing edges, nose cap,thermal blankets and belly-mounted tiles for signs of damage on FlightDay 2 of their missions

Analysisteams on Earth pored over the resulting data and, in both flights, gave thecrews follow-up targets for focusedinspections.

Thoseearlier images - which allowed mission managers for to clear Discovery'scurrent spaceflight to reentry - will be used as a baseline for analysis of thenew imagery from the STS-121 crew, NASA has said.

"We'regoing to evaluate and see if the data we get from it and the crew time requiredjustifies doing it for future flights," Ceccacci said.

Discoveryis currently slated to return to Earth after a 13-dayspaceflight on July 17. The orbiter is expected to land at 9:14 a.m. EDT(1314 GMT) at Runway 33 of the Shuttle Landing Facility at NASA's Kennedy Space Center in Cape Canaveral Florida.